1. Field of the Invention
The present invention relates generally to devices and methods for the treatment of female urinary incontinence, and more particularly, to an improved inserter and sheath combination particularly suitable for placing a sub-urethral sling.
2. Background Discussion
Women account for more than 11 million incontinence cases, with a majority of those women suffering from stress urinary incontinence (SUI). Women with SUI involuntarily lose urine during normal daily activities and movements, such as laughing, coughing, sneezing and regular exercise.
SUI may be caused by a functional defect or weakened tissue or ligaments connecting the vaginal wall with the pelvic muscles and pubic bone. Common causes include repetitive straining of the pelvic muscles, childbirth, loss of pelvic muscle tone, and estrogen loss. Such a defect results in an improperly functioning urethra. Unlike other types of incontinence, SUI is not a problem of the bladder.
Normally, the urethra, when properly supported by strong pelvic floor muscles and healthy connective tissue, maintains a tight seal to prevent involuntary loss of urine. When a woman suffers from the most common form of SUI, however, weakened muscle and pelvic tissues are unable to adequately support the urethra in its correct position. As a result, during normal movements when pressure is exerted on the bladder from the diaphragm, the urethra cannot retain its seal, permitting urine to escape. Because SUI is both embarrassing and unpredictable, many women with SUI avoid an active lifestyle and shy away from social situations.
One device and method for treating female urinary stress incontinence is described in detail in U.S. Pat. No. 5,899,909, which is incorporated herein by reference in its entirety. This patent discloses a surgical instrument comprising a shank having a handle at one end and connecting means at the other end to receive, one at a time, two curved needle-like elements which each are connected at one end to respective ends of a mesh intended to be implanted into the body. In practice, the mesh is passed into the body via the vagina first at one end and then at the other end, at one side and the other, respectively, of the urethra to form a loop around the urethra, located between the urethra and vaginal wall. The mesh is extended over the pubis and through the abdominal wall and is tightened. The mesh ends are cut at the abdominal wall, and the mesh is left implanted in the body. This trans-vaginal procedure is exemplified by the TVT product sold by Ethicon, Inc. of Somerville, N.J. In this procedure, two 5 mm needles pass a PROLENE mesh trans-vaginally and through the abdomen to create a tension-free support under the mid-urethra.
Sub-urethral slings have also been placed by a different approach wherein a needle is passed first though the abdominal wall along the same path as described above, and eventually exiting through the vaginal incision. The tape is then coupled to the needle in some manner, and pulled back through the body from the vaginal incision and out through the abdominal incision. The chosen approach, vaginal or abdominal, will often depend on the preferences of the surgeon.
Yet another approach for implanting a sub-urethral sling has more recently been developed in which the implanted sling extends from beneath the urethra out through the obturator hole on either side. This “transobturator” procedure may involve inserting an appropriately configured needle from a vaginal incision and subsequently out through the obturator hole, or vice versa. The former technique (an “inside-out” approach) and associated instruments are described in detail in U.S. Pat. Nos. 7,611,454, 7,204,802, and 7,261,723, and U.S. Patent Publication No. 2009/0306459, which are incorporated herein by reference in their entirety. As illustrated in U.S. Pat. No. 7,261,723, this technique may be performed using a surgical instrument including a surgical passer or introducer and tube elements applied over the ends of the surgical passers that are coupled to the tape to be implanted under the urethra.
One problem associated with products including a combination surgical passer and tube or sheath element is ensuring a proper fit between the surgical passer and tube element so that the tube element (which is coupled to the implant) is suitably secured to the surgical passer throughout the procedure, but can be readily removed from the surgical passer after it has been properly passed through the body to allow final placement of the implant. Previously known devices had either relied exclusively on a frictional or interference fit between the two pieces along at least a portion of their respective lengths, and/or some type of complementary interlocking recess/projection along their respective lengths of the type described in the '723 patent. For devices that rely exclusively on a frictional fit, they can either be subject to relative movement during the procedure if the friction connection is too weak, or otherwise be difficult or cumbersome for a surgeon to separate following passage of the surgical passer through the body. A complementary interlocking recess/projection requires a unique surgical passer and tube design that adds to the manufacturing and device costs of the product.
In an effort to overcome these disadvantages, one known device described in U.S. Patent Publication No. 2011/0230703, which is incorporated herein by reference in its entirety, discloses a simplified mechanism by which to secure the sheath element to a retaining device. The device described in this publication is also commercially available under the name GYNECARE TVT EXACT®, which is manufactured and sold by Ethicon, Inc. of Somerville, N.J. The retaining device of this known instrument is static resulting in a predetermined positioning of the distal end of the needle element relative to the distal end of the sheath element. It has been found, however, that improper use of this device (i.e., exposing the device to increased external force during passage through the body) can result in deformation of the tissue penetrating tip of the sheath element.
Thus, it would be desirable to provide a surgical assembly having improved resistance against such external forces at the distal end of the instrument.